[Bug target/97019] New: rs6000:redundant rldicr fed to lvx/stvx

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97019

            Bug ID: 97019
           Summary: rs6000:redundant rldicr fed to lvx/stvx
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: linkw at gcc dot gnu.org
  Target Milestone: ---

When we do the early expansion for altivec built-in function vec_ld/vec_st, we
can probably leave some redundant rldicr x,y,0,59 which aims to AND (-16) for
the vector access address, since the lvx/stvx will do the aligned and with -16
themselves, they are useless.

===== test case ====

extern int a, b, c;
extern vector unsigned long long ev5, ev6, ev7, ev8;

int test(unsigned char *pe) {
  vector unsigned long long v1, v2, v3, v4, v9;
  vector unsigned long long v5 = ev5;
  vector unsigned long long v6 = ev6;
  vector unsigned long long v7 = ev7;
  vector unsigned long long v8 = ev8;

  unsigned char *e = pe;

  do {
    if (a) {
      asm("memory");
      v1 = __builtin_vec_ld(16, (unsigned long long *)e);
      v2 = __builtin_vec_ld(32, (unsigned long long *)e);
      v3 = __builtin_vec_ld(48, (unsigned long long *)e);
      e = e + 8;
      for (int i = 0; i < a; i++) {
        v4 = v5;
        v5 = __builtin_crypto_vpmsumd(v1, v6);
        v6 = __builtin_crypto_vpmsumd(v2, v7);
        v7 = __builtin_crypto_vpmsumd(v3, v8);
        e = e + 8;
      }
    }
    v5 = __builtin_vec_ld(16, (unsigned long long *)e);
    v6 = __builtin_vec_ld(32, (unsigned long long *)e);
    v7 = __builtin_vec_ld(48, (unsigned long long *)e);
    if (c)
      b = 1;
  } while (b);

  v9 = v4;

  int p = __builtin_unpack_vector_int128((vector __int128_t)v9, 0);

  return p;
}

==== command ====
  -m64 -O2 -mcpu=power8

Currently the function find_alignment_op in RTL swaps pass cares the case where
have one single AND operation definition, we can extend it to check all
definitions are AND operations and aligned with -16B.